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Q. 104

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Precalculus Enhanced with Graphing Utilities
Found in: Page 487
Precalculus Enhanced with Graphing Utilities

Precalculus Enhanced with Graphing Utilities

Book edition 6th
Author(s) Sullivan
Pages 1200 pages
ISBN 9780321795465

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Short Answer

Show that the difference quotient for f(x)=cos xis given by

role="math" localid="1646431168099" f(x+h)-f(x)h=cos(x+h)-cos(x)h=-sin x·sin hh-cos x·1-cos hh

The difference quotient for f(x)=cos(x)is determined by using the Sum formula for the cosine function as

f(x+h)-f(x)h=cos(x+h)-cos(x)h=(cos x)(cos h)-(sin x)(sin h)-cos(x)h=-sin x·sin hh-cos x·1-cos hh

See the step by step solution

Step by Step Solution

Step 1. Given data 

The given function is

f(x)=cos x

the equation that needs to prove is

f(x+h)-f(x)h=cos(x+h)-cos(x)h=-sin x·sin hh-cos x·1-cos hh

Step 2. Derivation 

Use Sum formula for the cosine function

f(x+h)-f(x)h=cos(x+h)-cos(x)h=(cos x)(cos h)-(sin x)(sin h)-cos(x)h=-(sin x)(sin h)h-cos(x)-(cos x)(cos h)h=-(sin x)(sin h)h-(cos x)(1-(cos h))h=-sin x·sin hh-cos x·1-cos hh

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